Hong Kong -LRB- CNN -RRB- -- A nun has died after setting herself on fire in southwestern China , the first Tibetan woman known to have killed herself in this way , the London-based Free Tibet campaign group said Tuesday .

According to the group , Tenzin Wangmo , 20 , called for religious freedom in Tibet and for the return of the Dalai Lama as she set fire to herself outside Dechen Chokorling Nunnery in Ngaba County , Sichuan Province on Monday .

She died at the scene .

The State Administration for Religious Affairs in Beijing told CNN they were not aware of the incident .

Free Tibet , which advocates Tibetan independence , also reported that two Tibetans were shot and wounded on Sunday by security forces during a protest outside a police station in the prefecture of Ganzi .

Tenzin is the ninth Tibetan -- all monks or former monks -- to commit self-immolation in protest against Chinese rule since March , the advocacy group said . Five have died .

The last attempt took place on Saturday when a 19-year-old former monk from Kirti monastery in Aba , another ethnic Tibetan area in Sichuan province , set himself alight in the central market in Ngaba Town but survived .

His whereabouts are unknown , according to Free Tibet .

Activists say the disturbing acts reflect an increasingly repressive environment under Beijing 's control .

`` Most Tibetans live in fear because of suppressive and unfair government policies but they dare not speak up , '' prominent Tibetan writer and activist Tsering Woeser told CNN .

`` Tibetan Buddhists ca n't use violence to protest , therefore they can only do violence to themselves , such as self-immolation , to make people pay attention to their situation .

`` This is not suicide , this is sacrifice in order to draw the world 's attention . ''

Another incident in Aba in March , in which a monk died , sparked weeks of often violent confrontation between local monks and authorities . Security forces locked down the Kirti Monastery and eventually detained more than 300 monks , rights groups said at the time .

When the United Nations working group on enforced disappearances expressed its concern to Beijing , Chinese officials called the organization 's perspective `` biased and unfair . ''

`` The relevant local authorities are conducting legal education for the Kirti Monastery monks to maintain religious order there -- there was no question of forced disappearances , '' Hong Lei , a foreign ministry spokesman , said in June .

China also rejects accusations of oppression of Tibetans , saying its rule has greatly improved living standards for the Tibetan people .

The Dalai Lama 's representative signed an agreement with Beijing in 1951 to affirm China 's sovereignty over Tibet but also grant autonomy to the area . A failed uprising against Beijing 's rule in 1959 forced the Dalai Lama into exile .

The Dalai Lama denies seeking independence for Tibet , saying he wants genuine autonomy , under which Tibetans can make their own policies on key issues , such as religious practices .

In a 2008 uprising , violent unrest in Tibet and the subsequent military crackdown left at least 18 dead , and activists say tensions have remained high in many areas since then .

CNN 's Xiaoni Chen contributed to this report .

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Group : Tenzin Wangmo called for religious freedom in Tibet before setting herself alight

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Tenzin is the ninth Tibetan -- and first woman -- to commit self-immolation

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Free Tibet also reported that two Tibetans were shot and wounded during a protest

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Activists : Acts reflect an increasingly repressive environment under Beijing 's control